1. Field of the Invention
The present invention relates in general to computer printer font cartridges, and in particular, to a spring hook latching mechanism for a font cartridge extender which allows multiple font cartridges to be chained together as one operational unit.
2. Description of Related Art
In many personal computer systems, replaceable font cartridges are commonly used with printers, wherein each font cartridge contains information corresponding to a one or more character font sets. Most printers in common use, however, have only one or at most two receptacles for plugging in the font cartridges, which severely limits the selection of font sets available at any one time. When different font sets are desired, the existing font cartridge may be removed and a different one plugged in. Since the manufacturers of font cartridges decide which combinations of font sets to put into the font cartridges, it may not be possible for a user to have the selection of font sets he or she desires available on-line and installed in the printer at any one time, irrespective of how many font cartridges are owned. Thus, there is a need in the art for expansion modules which allow more than one font cartridge to be plugged into a printer receptacle.
One version of a font cartridge expansion module is shown in the co-pending U.S. patent application Ser. No. 07/632,530, filed Oct. 28, 1990, by Stephen Kurtin, and entitled "EXPANSION MODULE FOR COMPUTER PRINTER FONT CARTRIDGE," which is incorporated by reference herein. This patent discloses an expansion module which plugs into the font cartridge receptacle of a computer printer and into which a commercially available font cartridge can be plugged. Within the expansion module is a circuit board which has an edge connector at one end for plugging into the font cartridge receptacle of a printer, and a receptacle at the other end for receiving the edge connector of a font cartridge. The connector and receptacle within the expansion module are electrically connected so that a data bus which appears at the printer receptacle is coupled through to the font cartridge. The circuit board also contains sufficient read only memory (ROM) and other circuitry to store information about one or more character font sets, as desired. This information, as well as the information on the font cartridge plugged in to the expansion module, can be accessed by the printer through the data bus. When an expansion module with font cartridge attached is plugged into a printer receptacle, all of the font sets stored in the font cartridge and in the expansion module are available for use.
While the above-identified Kurtin reference describes the general concepts for font cartridge expansion modules, it does not provide a total solution. For example, the latching mechanism described in the Kurtin reference is not an optimal design The Kurtin reference describes a latching mechanism wherein the font cartridge is held to the expansion module by two spring catches on the sides of the case. Each catch is actuated by a ramp or slide button which rides in a slot cut in the side of case, and is operated by finger pressure applied to serrations on the button. When the slide button is slid down so that the rounded end of the catch slides up the ramp, the opposite end of the catch is forced against the inside of the case of the font cartridge. The end of the catch is beveled so that it bites into the case slightly to securely hold the font cartridge and expansion module together. The catch, which is preferably fabricated from spring steel strip stock, has sufficient stiffness so that when in a locked position it bites into the font cartridge slightly, but not enough to break it. A pin acts as a pivot around which the catch turns and a leaf spring provides a restoring force to cause the catch to release when the slide button is retracted.